- Make a field trip to the nearest river or stream and bring all the necessary materials and equipment already prepared for use:
- Take a sample with one of the sampling techniques:
- SIMPLE SAMPLING: Turn around stones and collect the attached benthos with tweezers or brush.
- SAMPLING WITH A NET: Take a net and hold it in water. Kick up the bottom of the stream in front of the net, to catch animals. With a brush, scrape animals from stones into the net. With swinging motions of the net through the water plants, capture animals hiding among plants.
- SAMPLING WITH MUD SCOOP: Take a mud scoop and take a full scoop of mud. Place the mud on a white tray together with some water and sort out the animals and place them into the sorting dish.
- PASSIVE SAMPLER: A passive sampler can be any object that can serve for the purpose of catching animals (i.e., a can, a tire, etc.). Carefully lower the passive sampler into the water. This is especially useful where the water is deep and difficult to sample with a net. Secure it to the bank and leave for at least two weeks so that animals can enter and colonize it. Then remove the sampler and brush the animals from the crevices on the stones to reveal the catch.
Use a thick plastic bottle, mark out diagonally across the bottle the area to be cut away from the plastic bottle that includes all of the base. Carefully cut along the line. Leave the top screwed on tightly. The volume of the whole scoop represents a standard sample.
- Animals can now be taken from the main white tray and separated. Sort the animals in a sorting dish. Try to identify them. You can help yourself with the Worksheet “Pollution detectives in rivers” or with a worksheet that was specifically prepared for your area, and with a book for identifying macroinvertebrates in your area. Count the animals of the same type and make a record. You will need the list of animals with their count in the lesson “Quality of surface water”.
- Take more samples at different locations. It is important to use exactly the same technique of sampling on each site to be able to compare the results. Remember to compare similar items, which means a lower section with a lower section of a river.
- Try to make photos of them, observe them and make drawings.
More information on aquatic macroinvertebrates:
(More information on basic compilation of methods for sampling is given in Schwoerbel, J. (1994): Methoden der Hydrobiologie. Süsswasserbiologie. 4. neubearbeitete Auflage, UTB 979, Gustav Fischer, Stuttgart, 368 pp. or in some other equivalent textbook.)
Activity adapted from Environmental Education Activities for Primary Schools – Suggestions for Making and Using Low Cost Equipment – Environmental Education Series 21. UNESCO International Center for Conservation Education, Cheltenham, 1992, Chapter 4 Water, Activity 4.8 Mud, glorious mud and Activity 4.9. Pollution detectives, p.60 – 63.